First returning Kirtland's warbler fledgling documented in Wisconsin

ADAMS COUNTY, Wis. - A Kirtland's warbler that hatched in Wisconsin last year and was banded before its first migration has returned to its birthplace in Adams County, providing a significant milestone in efforts to help boost populations of this federally endangered songbird, state and federal bird experts say.

"This is the first time we've been able to document that a bird hatched in Adams County has returned to the area," says Kim Grveles, a Department of Natural Resources avian ecologist. It's a very encouraging sign that Wisconsin is providing suitable and successful breeding habitat for these birds."

Chris Mensing, endangered species biologist with the U.S. Fish and Wildlife Service, also hailed the news. "It's exciting to see Kirtland's warblers returning to habitat in Wisconsin. With endangered species, you never want to put all your eggs in one basket. Having a successful breeding population outside the core Kirtland's warbler range in Michigan helps protect the species from catastrophic events."

The Kirtland's warbler was placed on the federal endangered species list about 40 years ago, when its population dropped to about 300 birds. Until 1995, Kirtland's warblers were found almost exclusively in the northern Lower Peninsula of Michigan and were struggling to recover from a steep decline in populations in the 1960s and 1970s due to habitat loss and trouble from the brown-headed cowbirds.

Starting in the late 1990s, the protections and efforts made under that federal law enabled the Kirtland's warbler to start expanding its breeding territory to Wisconsin, Michigan's Upper Peninsula and Ontario. The warblers have been observed in several counties in Wisconsin, and nests have been confirmed in Adams and Marinette counties. In 2012, Kirtland's warblers were recorded in five counties in Wisconsin (Adams, Douglas, Bayfield, Vilas, and Marinette), and a minimum of 24 singing male warblers were documented in the state.

The state Natural Resources Board in May approved adding the species to the state endangered species list because its numbers, while growing in Wisconsin, are still very small.

To help increase Kirtland's warblers in Wisconsin, DNR, the U.S. Fish & Wildlife Service and other partners now conduct annual surveys to listen and look for the birds, monitor nests in Adams County where breeding sites have been found, and set traps to keep cowbirds away from the warblers' nests.

Cowbirds lay their eggs in the nests of songbirds including Kirtland's warblers. The warblers are unable to recognize cowbird eggs or chicks as different from their own young. Cowbirds hatch earlier, are larger, and more aggressive at begging for food than warbler chicks, which results in the Kirtland's warbler parents raising a cowbird or two at the peril of their own brood.

The partners also are working to maintain and expand the mix of 5- to 20-year-old jack pine trees and barrens necessary by planting the tree species. Historically, such habitat depended on fire, Grveles says.

The 2013 annual survey for Kirtland's Warblers began on May 18 with 23 volunteers searching for Kirtland's Warblers in jack pine stands of six Wisconsin counties.

The returning bird was discovered in Adams County on June 3, 2013, by nest monitors Valarie Michel and Daryl Christensen. The bird had been hatched at the same site in 2012 and was captured and banded in August 2012 by Ron Refsnider and Joel Trick, both retired from US Fish and Wildlife Service.

Refsnider estimates the chances of finding this individual at the same site a year after hatching was less than 15 percent.

A small songbird that measures 5 ½ inches long and weighs under a half ounce.

Identifying marks:

The male has a bluish-gray back, black streaks on its yellow breast, and black eye lines and a black patch that make it look like it's wearing a mask. Females are less showy; they are brownish with faint streaks on their pale yellow breast.

Habits and habitats:

Kirtland's warblers nest only on the ground near the lower branches and in large stands of young jack pines 5 to 20 feet tall and 6 to 22 years old. The tree's age is crucial, although biologists are not sure why. It's possible the birds need low branches to help conceal their nests.

Population documented in Wisconsin

In 2012, Kirtland's warblers were recorded in five counties in Wisconsin (Adams, Douglas, Bayfield, Vilas, and Marinette), and we documented a minimum of 24 singing male warblers present in the state.